The present invention relates to an image generation method and a device used therefor for generating three-dimensional images to be drawn on a two-dimensional screen, such as on a television monitor; an image processing program for making a computer execute image generation processing; and a recording medium having recorded thereon such image processing program.
There are accelerating trends in higher integration and faster processing speeds of processors and memories in recent television game machines and personal computers which enable real-time generation of three-dimensional images with real presence and perspective in the display thereof on two-dimensional monitor screens.
When a three-dimensional image is drawn on a two-dimensional monitor screen, the three-dimensional polygon data are subjected to various geometric processing, such as coordinate conversion, clipping and lighting, and the resultant data are further subjected to translucent projection conversion.
In the conventional image generation device for generating a three-dimensional image to be displayed on a two-dimensional monitor screen, drawing of a semi-transparent object or drawing based on pixel occupational factors for anti-aliasing of the edge portion of an object generally requires so-called α-blending, which is a technique of generating a drawn image based on linear interpolation between pixel values on a frame buffer and drawn pixel values using a coefficient α for expressing semi-transparency (or transparency).
It has, however, been known for such technique of generating a drawn image based on α-blending that an image will look unnatural unless the objects are drawn in a manner such that the further the object is in the depth direction of the screen (direction of the depth from the viewpoint, referred to as Z direction hereinafter), the earlier it should be drawn. There is also known a technique for drawing objects according to their depth in the Z direction, such as a Z buffer method which can provide correct depth relation among the individual planes by finding out the closest planes for the individual pixels and expressing each pixel with a color of such closest plane. This is unlike the Z sorting method whereby the individual planes are painted with respective colors. With the Z buffer method, however, the foregoing problem remains unsolved.